Adding about a third of a cup of fruit or vegetables to your daily diet could cut your risk of developing type 2 diabetes by 25%, while higher consumptions of whole grains such as brown bread and oatmeal could cut the risk by 29%, according to two new studies published Wednesday in the journal BMJ.
The studies add to the growing database of literature that shows a healthier diet of whole grains, fruits and veggies -- along with regular physical activity, no smoking and maintaining a healthy weight -- can significantly impact your risk of developing the deadly disease.
Diabetes was the seventh leading cause of death in 2016, according to the World Health Organization, and is a "major cause of blindness, kidney failure, heart attacks, stroke and lower limb amputation."
Some 463 million adults between the ages of 20 and 79 years were living with diabetes in 2019, according to the International Diabetes Federation. That number is expected to rise to 700 million by 2045.
Objective look at fruits and veggies
Most studies use questionnaires to quiz study participants about what they ate and when, which leaves most nutritional studies subject to the vagaries of human recall.
But a group of European researchers used an objective measurement -- a composite score of blood biomarkers of vitamin C and carotenoids (the richly colored pigments of yellow, red and green on fruits and vegetables) -- to measure the amount of fruits and veggies eaten.
The study compared nearly 10,000 adults with new-onset type 2 diabetes to a group of nearly 14,000 adults who remained free of diabetes. All were participating in the European Prospective Investigation into Cancer and Nutrition (EPIC)-InterAct study that took place in eight European countries.
There was a 25% lower risk of developing type 2 diabetes for every 66 extra grams of fruit and vegetables eaten each day, the study found.
That's not much -- just over 1/3 cup of either fruits or veggies.
"The public health implication of this observation is that the consumption of even a moderately increased amount of fruit and vegetables among populations who typically consume low levels could help to prevent type 2 diabetes," the study said.
"It should be noted that these findings and other available evidence suggest that fruit and vegetable intake, rather than vitamin supplements, is potentially beneficial for the prevention of type 2 diabetes."
Whole grains good, except popcorn
The second study used questionnaires to measure the whole grain intake of more than 158,000 women and nearly 37,000 men taking part in the Nurses' Health Study, Nurses' Health Study II, and Health Professionals Follow-Up Study. All three studies have been following the health of Americans free from diabetes, heart disease and cancer over long periods of time.
Foods and ingredients considered whole grains were: whole wheat and whole wheat flour, whole oats and whole oat flour, whole cornmeal and whole corn flour, whole rye and whole rye flour, whole barley, bulgur, buckwheat, brown rice and brown rice flour, popcorn, amaranth and psyllium.
Results showed that eating two or more servings a week of oatmeal was associated with a 21% lower risk of diabetes, a 15% lower risk for added bran and a 12% lower risk for brown rice and wheat germ, when compared to eating less than one serving a month.
There was a 19% lower risk of diabetes with eating one or more servings a day of whole grain cold breakfast cereal and a 21% lower risk for the same amount of dark bread, again compared to eating less than one serving a month.
These statistics held true even after adjusting for body mass index and other lifestyle and dietary risk factors for diabetes, the study said.
On average, people who ate the most whole grains -- around four to six servings a week -- had a 29% lower rate of type 2 diabetes than those who ate none or less than one serving a month.
On a daily basis, reductions in risk plateaued at about two servings a day for total whole grain intake, and a half a serving a day for whole grain cold breakfast cereal and dark bread.
One grain, however, had a negative effect: popcorn. The study found an increased rate of type 2 diabetes with eating one or more servings of popcorn a day. The effect occurred only when a full serving of 1 cup or more was eaten.
While popcorn, as a whole grain, has relatively high amounts of fiber and fills us up, the researchers pointed out that Americans often eat their popcorn with lots of salt and butter, and sometimes sugar or cheese, which can lessen its healthy properties. In addition, most Americans don't pop from a whole grain but purchase "ultraprocessed" versions that are microwaved, home popped, or ready to eat.